In 1908, twenty years after having joined the newly created Institut Pasteur, Elie Metchnikoff shared the Nobel Prize in Physiology & Medicine with Paul Ehrlich. This prize was awarded to Metchnikoff for his discovery of phagocytes as the basis of cell-mediated immunity and to Ehrlich for his studies on antibodies and humoral immunity. Metchnikoff viewed phagocytosis within the wider concept of Harmony and Disharmony that described the complex relationship between pathogens and their hosts. One hundred years later, the importance of Metchnikoff's legacy is increasingly evident. Metchnikoff proposed that phagocytosis was an ancient mechanism originating in primitive metazoans that provided a rapidly operating defense system against microorganisms. Today, we know that phagocytes also plays a crucial role in adaptive immunity in higher organisms, thus reconciling Metchnikoff's cellular immunity with Paul Ehrlich's humoral immunity.